My earlier U.S. Pat. No. 7,159,251, describes a water saver toilet that maintains pressured air in a trapway passage that extends between upper and lower traps that are respectively connected to the toilet bowl and to a drain. The pressured air that is present between flushes, pushes water from the upper trap into the toilet bowl to maintain a larger spot of water in the toilet bowl, and uses the sudden drop of trapway air pressure during a flushing to enhance the flushing.
Applicant has found that a toilet of the type described in the above patent, occasionally loses all water in the upper trap. A thorough investigation shows that sometimes when someone applies a small amount of fluid or solid to the toilet bowl, as by urinating, and does not flush it, that small amounts of water flow out through the upper and lower traps along with some of the pressured air, without replenishment of the pressured air as would occur during a flushing. Such an event can result in the loss of substantially all air pressure in the trapway passage and in water in the upper trap siphoning out. The absence of water allows sewer gas to enter the bathroom. A way to prevent such inadvertent loss of air pressure and consequent siphoning, would be of value.